Semiconductor devices generate heat during their operation, and this heat usually acts to degrade the operation of the semiconductor device. For power semiconductor devices it is necessary to be cooled during operation to maintain acceptable device performance, and for high power semiconductors liquid cooling is often applied.
U.S. Pat. No. 5,841,634 discloses a liquid-cooled semiconductor device. The semiconductors are here placed inside a housing on a plate which is to be cooled. The device shows a fluid inlet port and a fluid outlet port, and a baffle placed in a chamber inside the housing. The baffle includes a wall separating the chamber into a top portion and a bottom portion, and walls separating each portion into compartments. A number of holes in the wall between top and bottom portion provide fluid communication between the portions. Fluid is led from the inlet port to a first bottom compartment, and then through holes to a first top compartment. In the top compartment the fluid is led along the plate to be cooled, and through holes to a second bottom compartment. From the second bottom compartment the fluid is led to a second top compartment, where it cools another area of the plate to be cooled. After having passed three top compartments the fluid it led to the fluid outlet port, and out of the device. Thus the cooling compartments of the device are connected in a serial manner.
DE 202 08 106 U1 discloses a cooling device, in particular for liquid cooling of semiconductor devices. The cooling device comprises a housing and a separate baffle positioned inside the housing and with a plurality of flow cells defined therein. The flow cells each form a fluid connection between an inlet manifold and an outlet manifold. DE 202 08 106 U1 does not disclose that the housing, the manifolds and the flow cells are formed in a single piece.
U.S. Pat. No. 6,101,715 discloses a microcooling device with a channel structure through which a coolant fluid can flow. The device shown in FIG. 1 comprises an inlet manifold, an outlet manifold and a plurality of flow channels manufactured in a single piece.
The flow channels are connected in parallel between the manifolds along one direction, i.e. the direction transversal to the flow direction. However, they are not arranged in parallel along any other direction. As a consequence, a temperature gradient would inevitably occur along the flow direction of the flow channels, and it would not be possible to tailor the cooling.
EP 0 447 835 concerning a cold plate and an integrated cooling module embodying a cross-hatch flow distribution scheme discloses a prior art cooling module in FIG. 3. This prior art cooling module comprises an inlet and an outlet, and a meandering flow channel establishing a fluid connection between the inlet and the outlet. The flow channel is provided with fins in order to create turbulence in the cooling fluid. Since there is only one flow channel, the cooling is serial, and a temperature gradient will therefore occur.
As the fluid passes the first top compartment, it takes up heat from the plate to be cooled and thus leaves the first top compartment at a higher outlet temperature than the inlet temperature. When the fluid then reaches the second top compartment, additional heating of the fluid will take place, and this will lead to a temperature difference on the cooled plate, from fluid inlet port end to fluid outlet port end. This is detrimental to the lifetime of such a power semiconductor device as high power semiconductors are very sensitive to temperature variations and also sensitive to the general temperature level.
Also the serial connection of multiple cooling compartments will have a high flow resistance as a result, leading to a high pressure drop or a low flow rate of the fluid through the cooling device.
WO 02/055942 discloses a normal-flow heat exchanger comprising a core having a heat-transfer surface. An inlet plenum is located at one end of the length of the core, and an outlet plenum is located at the opposite end of the length. A plurality of inlet manifolds extend the length of the core, and a plurality of outlet manifolds extend the length of the core and are located alternatingly with the inlet manifolds across the width of the core. A plurality of interconnecting channels each fluidly communicate with a corresponding inlet manifold and the two outlet manifolds located immediately adjacent that inlet manifold. In order to provide the manifolds and the interconnecting channels, it is necessary to manufacture the heat exchanger in several plates which are subsequently assembled to form a unitary structure. In order to obtain a tight fit between the individual plates, it is necessary to manufacture each plate in a very precise manner. This is a disadvantage because it is very difficult and expensive to obtain sufficient accuracy. Consequently the unit price for the heat exchanger becomes relatively high.